COMPUTER-SIMULATION OF PORTEVIN-LECHATELIER EFFECT BASED ON STRAIN-SOFTENING MODEL

A new phenomenological theory for the Portevin-LeChatelier effect is p roposed. The theory is based on an unknown internal stress Y-ir which decreases with strain (work softening) and increases with time (age ha rdening). Y-ir is introduced to satisfy the negative rate sensitivity (n.r.s.) of flow stress and it is supposed to be due to very fine clus ters which are cut by dislocation and restored by solute atom diffusio n. Almost all constants used in the theory can be determined by tensil e test. The results of simulation can explain the effect of temperatur e, strain and strain rate on the onset strain of P-L effect. Especiall y, the model can explain the no-occurrence of P-L effect under the n.r .s. condition in aged Al-Cu alloy, and the quantity of transition stra in in tensile test in which the crosshead speed is abruptly changed. ( C) 1997 Elsevier Science S.A.